A NodeB needs to control uplink transmission power so as to acquire optimal uplink transmission power in Release 8/Release 9 of Long Term Evolution (LTE). The NodeB may measure uplink pass loss of a terminal so as to acquire a compensation value of the uplink path loss, and finally determines, according to factors including an interference measurement result of the NodeB, the receiving sensitivity of the NodeB, reduction in interference to an adjacent cell and so on, a power control factor for controlling the terminal to perform uplink transmission.
A carrier for aggregation in a Carrier Aggregation (CA) system is called a Component Carrier (CC) and is also known as a cell. In the meanwhile, the concepts of a Primary Component Carrier/Cell (PCC/PCell) and a Secondary Component Carrier/Cell (SCC/SCell) are also proposed. A CA-supported system at least includes a PCC and an SCC, wherein the PCC is always in an activated state.
The introduction of a CA technology enables a plurality of Physical Uplink Shared Channels (PUSCH) to perform transmission simultaneously on different CCs, and a PUSCH and a Physical Uplink Control Channel (PUCCH) may also perform transmission simultaneously on the same or different CCs.
In LTE and Long Term Evolution-Advanced (LTE-Advanced or LTE-A) systems, Uplink Control Information (UCI) includes downlink transmission Acknowledgement/Negative Acknowledgement (ACK/NACK), downlink physical Channel State Information (CSI) and an uplink Scheduling Request (SR). The UCI may support 5 downlink CCs. An uplink transmission multiplexing rule of UCI is partly summarized as follows according to LTE standard 36.213 (Physical layer procedures Release 11) of Release 11 of the 3rd Generation Partnership Project (3GPP).
All UCI multiplexed on a PUCCH is only transmitted on a PCC of a PCell.
When simultaneous transmission of a PUCCH and a PUSCH is not supported, and at least one PUSCH performs transmission, UCI is multiplexed on one PUSCH. Generally, Periodic CSI (P-CSI) and/or ACK/NACK are/is transmitted on a PUSCH of a PCC. If the PUSCH of the PCC does not exist while a PUSCH of an SCC exists, the UCI is multiplexed on the PUSCH of the SCC. If a plurality of SCC PUSCHs exists on one sub-frame, the P-CSI and/or ACK/NACK are/is transmitted on an SCC PUSCH having the smallest cell index.
When simultaneous transmission of a PUCCH and a PUSCH is supported, and at least one PUSCH performs transmission, ACK/NACK is transmitted on the PUCCH. Generally, P-CSI is transmitted on a PCC PUSCH. If the PCC PUSCH does not exist while a PUSCH of an SCC exists, the P-CSI is multiplexed on the SCC PUSCH. If a plurality of SCC PUSCHs exists on one sub-frame, the P-CSI is transmitted on an SCC PUSCH having the smallest cell index.
Limited by the UCI multiplexing rule, UCI of an evolved Node B (eNodeB) may be multiplexed and transmitted on an uplink CC of another eNodeB, and the latter further transmits UCI to the former through backhaul between the eNodeBs.
In a CA-supported system, uplink power is controlled based on the UCI multiplexing rule. An eNodeB performs uplink scheduling according to Power Headroom Reporting (PHR) of a User Equipment (UE) so as to allocate an uplink transmission resource, a Modulation and Coding Scheme (MCS) and transmission power for each CC. However, the sum of the transmission power of the CCs may still exceed the maximum total transmission power allowed by the terminal/UE. In this case, the UE needs to reduce the power.
According to LTE standard 36.213 of Release 11, when a PUCCH and a PUSCH not carrying UCI performs transmission simultaneously, the transmission power of a PUSCH of each CC is reduced according to the same proportion factor if the total transmission power of a UE exceeds the maximum transmission power. When a PUSCH carrying UCI performs transmission on a certain cell while PUSCHs not carrying UCI perform transmission other cells, the power of the carrier PUSCHs not carrying UCI is reduced according to the same proportion factor if the total transmission power of the UE exceeds the maximum transmission power. If a PUSCH and a PUCCH carrying UCI perform transmission simultaneously on a certain cell while PUSCHs not carrying UCI perform transmission on other cells, the power required by the PUCCH is allocated for the PUCCH first if the total transmission power of the UE exceeds the maximum transmission power, and the remaining power, if any, is allocated to the PUSCH carrying UCI. If there is still remaining power, the power of the carrier PUSCHs not carrying UCI is reduced according to the same proportion factor, and the reduced power does not exceed the remaining power.
The uplink power reduction control method is designed for an existing UCI multiplexing rule of a CA system, and backhaul between double-link eNodeBs is unsatisfactory and has a long time delay. Uplink UCI of different eNodeBs needs to be independently transmitted to corresponding eNodeBs, thus a UCI multiplexing rule is different from the existing CA system multiplexing rule. For example, UCI (ACK/NACK, CSI, or SRs) of different eNodeBs may be transmitted simultaneously on CCs of their respective eNodeBs. The UCI may be multiplexed on two PUCCHs or PUSCHs of different eNodeBs on the same sub-frame or transmitted by other channel combination forms different from those specified by the existing UCI multiplexing rule. Besides, since some uplink control information and scheduling information can be hardly interacted in real time between two double-link nodes, NodeBs fail to acquire the scheduling information, and only uplink data and control information corresponding to one NodeB are transmitted on some sub-frames while uplink data and control information corresponding to two NodeBs are transmitted on some sub-frames. At the moment, since the two NodeBs perform power control independently, the power of transmission on two uplink sub-frames may exceed the maximum transmission power of a terminal. For a CA mechanism, since a plurality of CCs are located on the same node or different nodes with ideal backhaul, and scheduling information is interacted in real time, a NodeB may approximately calculate sub-frames on which the power of the terminal exceeds the maximum value, and limits reception of uplink data and control information on the corresponding sub-frames according to a standard of the terminal, thereby ensuring the receiving accuracy of the NodeB.
However, a NodeB fails to perform corresponding estimation and reception with a terminal due to the absence of ideal backhaul in a double-link scenario, thus resulting in receiving errors of uplink data and control information, and affecting the average spectral efficiency of the system.
Therefore, there is uplink transmission against the existing CA system UCI multiplexing rule in double links. The existing uplink power reduction method fails provide a solution if the total power of different CCs exceeds the maximum total transmission power allowed by a UE, and it is necessary to redesign a new method for controlling uplink power.
At present, there is not effective solution for the problem in the related art that an uplink power reduction method cannot ensure uplink transmission reliability in a double-link scenario.